The present invention relates to a motor assembly for a vehicle air conditioner, which assembly includes a motor and a control circuit device integrally assembled with the motor. More particularly, the present invention pertains to a motor assembly for a vehicle air conditioner, which assembly has a structure that prevents a control circuit device from being wet.
For example, Japanese Patent No. 3157567 discloses a motor assembly for a vehicle air conditioner, which assembly includes a motor and a fan. The motor drives rotary shaft that protrudes upward. The fan is coupled to the rotary shaft. As the rotary shaft rotates, the fan causes air above to flow in radially outward directions. In such a motor assembly, the motor is located in an air conditioning chamber while being held by a motor holder. The motor assembly creates airflow in the air conditioning chamber with the fan, thereby drawing air outside or inside the vehicle and sending the air into the passenger compartment. The above described patent publication discloses a structure for preventing the interior of the motor from being wet.
On the other hand, to improve the passenger comfort, the rotation speed of the motor needs to be arbitrarily controlled. The rotation speed of the motor is controlled by a switching device such as a power transistor and a MOS field effect transistor (FET). When the motor rotation speed is controlled by using a switching device, a protection circuit for protecting the switching device needs to be provided to securely control the current (or voltage) of the motor assembly.
Japanese Laid-Open Patent Publication No. 2000-316247 discloses a motor assembly for a vehicle air conditioner, which assembly has a control circuit device and a fan. The assembly also includes a blower case attached to an upper side of a motor holder, and a lower case attached to a lower side of the motor holder. A waterproof structure of the motor assembly is constructed by providing a notch in a boundary section between the motor holder and the lower case. If air that has been drawn into the motor assembly contains water, some of the water advances along the gap between the motor holder and the lower case, and is then guided to the outside of the motor assembly through the notch formed in the boundary section. As a result, the control circuit device is prevented from being wet with water that enters inside the motor assembly.
However, in the motor assembly disclosed in the publication No. 2000-316247, the notch in the boundary section produces a hole. Therefore, if water fails to be guided to the outside of the assembly through the notch, the water can enter the interior of the motor and cause the control circuit device to be wet. Further, water that exits the assembly through the boundary section can flow along the outer surface of the motor holder or the lower case, and enter the motor through the hole, causing the control circuit device to be wet.
Further, water that exits the assembly through the boundary section between the blower case and the motor holder can flow along the outer surface of the motor holder, and enter the interior through the boundary section between the motor holder and the lower case, causing the control circuit device to be wet.
The motor is located in a position that communicates with an outside air inlet. Thus, when, the vehicle is washed in a car wash and water is applied to the outside air inlet with a high pressure, the water can enter the outside air inlet. This causes connecting members such as wires that electrically connect the control circuit device with the motor to be wet with water droplets. Further, in some cases condensation occurs due to the difference between the temperature of the passenger compartment and the outside temperature, which can result in water droplets collected on the connecting members. The water droplets on the connecting members can then flow along the members and reach the control circuit device.